CN110110416B - Distributed energy source cold network cold supply optimization method based on graph theory - Google Patents
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Abstract
The invention discloses a graph theory-based distributed energy source cold supply network cold supply optimization method, which comprises the following specific steps: constructing a space topological structure of a cold water pipe network according to actual user conditions; generating an upper incidence matrix from a spatial topology using graph theory principles
With lower associative matrixA(ii) a Establishing a node heat flow balance equation and a directed pipe section heat flow balance equation; inputting the initial condition of the heating power working condition of the cold network under the design working condition; solving the matrix equation set of the cooling network heating power working condition calculation model by using a Gaussian elimination method to obtain the heating power working condition adjusting condition of each node, and adjusting the cooling network according to parameter changes when the outdoor temperature is adjusted or the local working condition of the cooling network is adjusted to ensure that the heat provided by the cooling network is consistent with the cooling load of a user so as to optimize a cooling network cooling system and achieve the effect of optimizing energy conservation. The method can conveniently calculate and analyze the thermodynamic working condition of the distributed energy source cold network system so as to adjust and optimize the cold supply system for the cold network and enable the cold network to operate in an energy-saving mode.
Description
Technical Field
The invention relates to the field of distributed energy, in particular to a graph theory-based distributed energy cold net cold supply optimization method which can be suitable for adjusting a distributed energy cold net system requiring long-time cold supply in southern regions of China.
Background
The combined cooling, heating and power supply belongs to the category of distributed energy systems, is the main direction and form of the development of distributed energy, and compared with the traditional central air-conditioning refrigeration system, the distributed energy cold net has the advantages of high comprehensive utilization efficiency of energy, capability of effectively improving the thermal environment of regional buildings, environmental friendliness and the like, and is the development direction of the air-conditioning system of regional building groups in the future. However, due to the large cooling load, large scale, large number of devices and complex system in the area, the users have different requirements for the supply of the cooling network and have different timeliness at the user side, so that the distributed energy source cooling network system is in a variable working condition operation state under most conditions, and the operation optimization and control technical level is the key for determining the operation energy efficiency of the distributed energy source cooling network and whether the energy-saving optimal energy can be exerted.
The matching problem of the cold quantity provided by the cold network to the user and the cold load of the user is a problem which needs to be solved urgently in engineering, and when the cold quantity provided by the cold network is larger than the cold load of the user, energy is wasted; otherwise, the refrigeration requirement of the user can not be met. In the existing calculation method, different calculation models are used according to different user distribution structures, and great inconvenience is brought to modeling work. In addition, the prior art can not well analyze the regulation rule and the regulation characteristic of the thermal working condition caused by the regulation of the local working condition of the cold net, and when the local working condition is regulated, the flow of cold water can not be monitored and regulated in time, so that the problems of hydraulic imbalance and thermal imbalance are caused.
Therefore, it is necessary to provide a distributed energy source cold supply optimization method to provide a basis for dynamic adjustment and optimization of the distributed energy source cold supply network system, and to realize optimal operation and energy-saving operation of the cold supply network system.
Disclosure of Invention
The invention provides a cold supply optimization method of distributed energy cold network based on graph theory, aiming at solving the problems of cold network operation energy efficiency reduction and energy-saving economy caused by outdoor temperature adjustment or cold network local working condition adjustment of the distributed energy cold network, and aiming at calculating the temperature of each node, the cold user fan coil outlet water temperature, the cold network return water temperature and the dynamic adjustment condition of the total load of a cold source so as to calculate and analyze the thermodynamic working condition of the distributed energy cold network system, adjusting the cold network according to parameter change and enabling the heat provided by the cold network to be consistent with the user cold load so as to optimize the cold supply system of the cold network and achieve the effect of optimizing energy saving
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a graph theory-based distributed energy source cold supply network cold supply optimization method, which comprises the following steps of:
s1, constructing a cold water pipe network space topological structure of the distributed energy cold water pipe network with the number of pipe sections being X and the number of nodes being Y +1 according to actual user conditions;
s2, generating an upper incidence matrix related to the hydraulic and thermal parameters of the inflow nodes by using the graph theory principle according to the space topological structure established in the step S1
Lower correlation matrix related to hydraulic and thermal parameters of outflow nodeA；
S3, establishing a node heat flow balance equation and a directed pipe section heat flow balance equation according to the upper and lower incidence matrixes generated in the S2, and establishing a mathematical model;
s4, determining the initial condition of the cold net under the thermal condition according to the design condition;
s5, solving a matrix equation set of the cooling network thermal condition calculation model by using a Gaussian elimination method to obtain the thermal condition adjustment condition of each node;
s6, when outdoor temperature is adjusted or local working conditions of the cold net are adjusted, the total circulating flow of the cold net is controlled in an optimized mode, the backwater temperature of the whole cold net is guaranteed to be kept at the design temperature, and therefore cold using requirements of users can be met, the effect of optimizing energy conservation can be achieved, and further the whole cold net cold supply system is optimized;
and S7, when the outdoor temperature is adjusted or the local working condition of the cold net is adjusted, repeating the steps of S4-S6, calculating the thermal working condition adjustment condition of each node, and adjusting the operation of the cold net system according to the parameter change to achieve the effect of optimizing energy conservation.
Preferably, in step S1, the spatial topology structure of the cold water pipe network is composed of a cold source, a water supply pipe network, a water return pipe network, and a cold user;
preferably, in step S2, the upper correlation matrix
Is a matrix of the order of Y X X,
for the upper association matrix
If cold fluid flows into the associated node i through directed pipe segment j, then the matrix is associated at the upper level
In (1),
otherwise
1≤i≤Y,1≤j≤X
The lower incidence matrixAIs a matrix of the order of Y X X,
for lower association matrixAIf cold fluid flows out of the associated node i through directed pipe segment j, then the matrix of associations is in the lowerAIn (b) ij 1 is ═ 1; otherwise
1≤i≤Y,1≤j≤X；
The hydraulic parameter is flow Q, the thermal parameter is temperature T,
multiplied by the pipe segment parameter column vector, equal to the parameter column vector flowing into each node,Amultiplied by the column direction of the pipe section parameterThe quantity is equal to the parameter column vector of each node;
preferably, in the step S3, the node heat flow balance equation is:
in the formula
The sum of the heat flows of the associated branches into the associated nodes; q is the heat flow column vector flowing into the associated node from the directed pipe segment, q ═ q (q) 1 ,q 2 ,…,q j ,…,q X ) T ，q j The heat flow which flows into the associated node from the directed pipe section j is shown, and the heat flow takes a positive value;A(q- γ) is the sum of the heat flows out of the associated node for the associated leg; gamma is the input or output cold load column vector on the directed pipe section, gamma is (gamma) 1 ,γ 2 ,…,γ j ,…,γ X ) T ，γ j The input or output cold load on the directed pipe section j is positive, and the output is negative;
q is represented by the formula: q ═ G c T c
In the formula T c Is a column vector of temperature at the end of a directed pipe section, T c ＝(t c1 ,t c2 ,…,t cj ,…,t cX ) T ，t cj Indicating the temperature of the j end of the directed pipe section; g c Is X diagonal matrix with diagonal element G jc Is the product of the pipe section flow j and the cold fluid specific heat capacity, i.e. G c ＝diag(G 1c ,G 2c ,…,G jc ,…,G Xc ) T 。
γ is represented by the formula: y ═ H (T) w -A T T)
Wherein H ═ diag (H) 1 ,h 2 ,…,h j ,…,h X ) Is an intermediate variable matrix, and in the cold user section, H is related to the comprehensive heat transfer coefficient of the building, the heat transfer area of the building and the air flow passing through the outer side of the fan coil, H j Is a middle changeElements of the quantity matrix H in sections H not connected to cold users j 0; t is a cold grid node temperature column vector, and for a network line graph with Y +1 nodes, the cold grid return water temperature is generally selected as the reference node temperature, and then T ═ T (T ═ T) 1 ,t 2 ,…,t Y ) T ,t i Is the cold mesh node i temperature; t is a unit of W Is the outdoor temperature column vector, X X1 order, T W ＝(t w ,t w ,…,t w ,…,t w ) T ，t w Expressed as the outdoor temperature. (ii) a
Preferably, in step S3, the directed pipe segment heat flow balance equation is divided into three parts:
the first part, on the premise of not counting heat loss of the pipe section, except for the cold source of the cold supply system or the pipe section where the cold user is located, the end temperature of the directed pipe section is the initial end temperature of the directed pipe section, namely:
DA T T＝DT c
wherein D is diag (D) 1 ,d 2 ,…,d j ,…,d X ) As a matrix of intermediate variables, d j Is the element in the intermediate variable matrix D, when the element is the pipe section of the system cold source or the refrigeration user, D j Not more than 0, otherwise, d j ＝1；
And in the second part, for the pipe section where the cold net user is located, the cold net cooling capacity is equal to the cold load of the user, namely:
H(T w -A T T)＝EQ c (T c -A T T)
wherein E is diag (E) 1 ,e 2 ,…,e h ,…,e X ) As a matrix of intermediate variables, e j As elements of the intermediate variable matrix, e when the section of the pipe in which the refrigeration user is located j 1, otherwise, e j ＝0；T W Is an outdoor temperature column vector; q c For the circulation water flow of the cold user, the initial value is the design circulation water flow Q for the cold user c0 According to the adjustment parameter pair Q c The change is made so as to achieve the purpose of adjusting the cold net.
The third part, to the pipeline section that the system cold source belongs to, it has to the pipeline section end temperature equals cold source export water supply temperature, also when not counting cold volume loss of cold net pipe section, cold net water supply temperature, also be cold user entry temperature promptly:
MT g ＝MT c
wherein, T g ＝(t g ,t g ,…,t g ,…,t g ) T Is a Y x 1 order matrix, t g Water supply temperature for cold net, M ═ diag (M) 1 ,m 2 ,…,m j ,…,m X ) Is a matrix of intermediate variables, m j Is an element in the intermediate variable matrix, and when the element is a pipe section where a cold source of the system is positioned, m is j 1, otherwise, m j ＝0；
Preferably, in step S4, the cold net thermodynamic condition calculation initial condition includes: the method comprises the steps of changing the water supply temperature of a front cooling network, changing the water return temperature of the front cooling network, changing the indoor temperature of a front cooling user, changing the outdoor temperature of the front cooling user, designing the circulating water flow of a single cooling user, designing the cooling load of the single cooling user, the comprehensive heat transfer coefficient of the building, the heat transfer area of the building and the air flow passing through the outer side of a fan coil, wherein the water temperature of an outlet of the fan coil of the front cooling user is consistent with the water return temperature of the front cooling network.
Preferably, in step S5, the node heat flow balance equation and the directed pipe section heat flow balance equation form a matrix equation set including X + Y independent equations, and according to the known conditions in step S4, the number of unknowns in the matrix equation set is X + Y, and because of the correlation matrix
AndAthe system is determined by a topological structure, so that the equation set has a unique solution; the Gaussian elimination method is used for solving the solution of the linear equation set to obtain the indoor average temperature of the changed cold user, the outlet water temperature of the fan coil of the cold user, the return water temperature of the changed cold network and the adjustment condition of the total load of the cold source, the adjustment condition of the total load of the cold source is estimated according to the return water temperature of the changed cold network, and the Gaussian elimination method saves more time as the equation is more.
Preferably, in step S6, after the temperature of the supply and return water is determined after the cold net is changed, the total circulation flow rate supplied by the cold net is changed along with the change of the cold load, and the calculation formula is as follows:
in the formula Q c total Is the total circulation flow of the cooling network, W s The cooling load supplied to the cooling network, C Water (I) Is the specific heat capacity of water, t g ，t h Respectively the supply water temperature and the return water temperature after the cold net is changed.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention can solve the matching problem of the cold quantity required by the users of the cold network and the cold quantity supplied by the cold network, avoid the heat imbalance and realize the optimization of the operation of the cold network system.
2. Based on graph theory, the invention enables the cooling pipe networks with different geometric structures to use a uniform calculation model, thereby greatly simplifying the modeling process.
3. The invention can analyze the regulation of the heating power working condition of the whole pipe network model caused by the regulation of the local load through the calculation method so as to properly regulate the cold network and avoid heating power imbalance.
Drawings
FIG. 1 is a computational flow diagram of the method of the present invention;
FIG. 2 is a schematic diagram of a spatial topology of a cold water pipe network according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the flow rate of circulating water for each cold user in the embodiment of the present invention;
FIG. 4 is a schematic view of the water temperature at the outlet of the fan coil of each cold user in the embodiment of the present invention;
FIG. 5 is a schematic diagram of the return water temperature of the cold net in the embodiment of the invention;
FIG. 6 is a schematic diagram of the return water temperature of the cold net in the embodiment of the invention;
Detailed Description
The invention is described in detail below with reference to the figures and the detailed description of the invention.
First, a calculation simulation flowchart is explained, and fig. 1 is a calculation flowchart of the entire method, which specifically includes: firstly, a cold water pipe network space topological structure is constructed according to the actual user condition, and then an upper incidence matrix related to hydraulic and thermal parameters flowing into a node is generated according to the space topological structure by utilizing the graph theory principle
Lower correlation matrix relating to hydraulic and thermal parameters of outflow nodeAThen, a node heat flow balance equation and a directed pipe section heat flow balance equation are established according to the generated upper and lower incidence matrixes, and at the moment, the establishment of a cooling network heating power working condition calculation mathematical model is completed; and then inputting the thermal working condition of the cold network under the design working condition as the initial condition of the model, and solving a matrix equation set of the calculation model of the thermal working condition of the cold network by using a Gaussian elimination method so as to obtain the adjustment conditions of the indoor average temperature of the cold user, the outlet water temperature of a fan coil of the cold user, the return water temperature of the cold network and the total load of a cold source.
Taking the distributed energy cold network system as an example for supplying cold to 10 users, the method is adopted to calculate the heating power working condition of the cold network, and under the design working condition, the water supply temperature t is changed after the day cold network is changed g 6 ℃ and the return water temperature t after the cold net is changed h 13 deg.C, cold user indoor temperature t s 25 deg.C, cold outdoor temperature t w 32 deg.C, single user designed circulating water flow rate Q c ＝180m 3 And h, the single user design cooling load q is 1.46 MW.
Fig. 2 is a schematic diagram of a spatial topology structure of a 10-user cold water pipe network in an embodiment of the present invention, including 1 cold source, 10 cold users, 31 directed pipe segments, and 22 nodes. The upper correlation matrix in this embodiment
A 21 x 31 order matrix, with the cold fluid flowing through directed pipe segment j into associated node i, then
Otherwise
(i is more than or equal to 1 and less than or equal to 21, j is more than or equal to 1 and less than or equal to 31), and the lower correlation matrixAA 21 x 31 order matrix, with cold fluid flowing out of the associated node i through directed pipe segment j, then
Otherwise
(1≤i≤21,1≤j≤31)。
The satisfied node heat flow balance equation is as follows:
in the formula T c Is a column vector of temperature at the end of a directed pipe section, T c ＝(t c1 ,t c2 ,…,t cj ,…,t c31 ) T ；G c Is 31X 31 diagonal matrix, and the diagonal element is the product of pipe section flow and cold fluid specific heat capacity, namely G c ＝diag(G 1c ,G 2c ,…,G jc ,…,G 31c ) T ；H＝diag(h 1 ,h 2 ,…,h j ,…,h 31 ) Is an intermediate variable matrix; t is cold net node temperature column vector, and T is (T) 1 ,t 2 ,…,t 21 ) T ；T W Is an outdoor temperature column vector of 31 x 1 order, T W ＝(32,32,…,32) T ；
The heat flow balance equation of the satisfied directed pipe section is as follows:
DA T T+H(T w -A T T)+MT c ＝DT c +EG c (T c -A T T)+MT g
wherein D is diag (D) 1 ,d 2 ,…,d j ,…,d 31 )，E＝diag(e 1 ,e 2 ,…,e j ,…,e 31 )，H＝diag(h 1 ,h 2 ,…,h j ,…,h 31 )，M＝diag(m 1 ,m 2 ,…,m j ,…,m 31 ) And the fourth is an intermediate variable matrix; t is g Temperature of water supplied to cold net, T g ＝(t g1 ,t g2 ,…,t gj ,…,t g31 ) T ；T c Is a column vector of temperature at the end of a directed pipe section, T c ＝(t c1 ,t c2 ,…,t cj ,…,t c31 ) T ；G c Is 31 x 31 diagonal matrix, and the diagonal element is the product of pipe flow and cold fluid specific heat capacity, i.e. G c ＝diag(G 1c ,G 2c ,…,G jc ,…,G 31c ) T ；H＝diag(h 1 ,h 2 ,…,h j ,…,h 31 ) Is an intermediate vector; t is cold net node temperature column vector, T ═ T 1 ,t 2 ,…,t 21 ) T ；T W Is an outdoor temperature column vector of 31 x 1 order, T W ＝(32,32,…,32) T ；
The node heat flow balance equation and the directed pipe section heat flow balance equation form a matrix equation set containing 31+21 independent equations, and according to the known conditions in the step S4, the number of unknowns in the matrix equation set is 31+21 at the moment, and because of the incidence matrix
AndAdepending on the topology, the system of equations has a unique solution. Solving the solution of the linear equation set by a Gaussian elimination method to obtain the indoor average temperature of the changed cold user, the outlet water temperature of the fan coil of the cold user, the return water temperature of the changed cold network and the adjustment condition of the total load of the cold source, wherein the adjustment condition of the total load of the cold source is calculated according to the return water temperature of the changed cold network, as shown in the attached figures 3, 4 and 5.
(1) From fig. 3, the hydraulic regulation condition after the user 6 is turned off can be obtained, when the user 6 is turned off, the flow rates of the circulating water of other users are increased, and the flow rate is increased as the user is farther away from the cold source.
(2) From figure 4, the adjustment of the temperature at the outlet of each user fan coil before and after user 6 has been turned off can be obtained. When the user 6 closes, the outlet temperature decreases significantly, and the magnitude of the decrease in outlet temperature decreases as the user increases in distance from the cold source. This is determined by the hydraulic conditions of the cold net. The farther away from the cold source, the smaller the circulation flow, and when the design load of a single user is unchanged, the total heat exchange amount is unchanged, the flow is reduced, and the temperature difference is increased.
(3) The adjustment of the return water temperature of the cold net before and after the user 6 is closed can be obtained from fig. 5. When the user 6 is closed, the return water temperature of the cold net is obviously reduced from the original 13 ℃ to 12.2811 ℃, so that the cold load of the whole cold net can be calculated, the adjustment is carried out, and the effect of energy-saving operation is achieved.
(4) Fig. 6 is a trend graph of the return water temperature of the cold net with the total circulation flow when the user 6 is closed. It can be seen from the graph that the cold net return water temperature does not vary linearly with the total circulation flow. When the requirement of the return water temperature of the whole cold net is known (for example, the requirement of the design return water temperature of the embodiment is 13 ℃), the total circulating flow of the cold net can be optimized, so that the cold requirement of a user can be met, and the aim of saving energy can be fulfilled. After user 6 turns off, 500m 3 The return water temperature of the whole cold network is lower (lower than the design temperature) due to the inlet flow of the cold source per hour, and when the total circulation flow of the cold network is reduced to 448 and 449m 3 At the time of the reaction, the temperature of the whole backwater rises to 13 ℃. From this data, 448-449m was obtained 3 The total circulation flow per hour can meet the cold demand of each user and achieve the effect of energy conservation.
The above example is described by taking a distributed energy source cold network system as a representative, but the distributed energy source cold network cooling optimization method based on the graph theory is theoretically applicable to other multi-user environments.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (7)
1. A distributed energy source cold supply network cold supply optimization method based on graph theory is characterized in that an upper correlation matrix and a lower correlation matrix are introduced through a graph theory method to establish a cold supply network thermal working condition calculation mathematical model, a node heat flow balance equation and a directed pipe section heat balance equation are solved, so that the temperature of each node, the cold user fan coil outlet water temperature, the cold supply network return water temperature and the dynamic adjustment condition of the cold source total load are obtained, the cold supply network is adjusted according to parameter change, the heat provided by the cold supply network is consistent with the user cold load, the cold supply network cold supply system is optimized, and the purpose of energy-saving operation is achieved; the method comprises the following steps:
s1, constructing a cold water pipe network spatial topological structure of the distributed energy cold water pipe network with X pipe sections and Y +1 nodes according to the actual user condition;
s2, generating an upper incidence matrix related to the hydraulic and thermal parameters of the inflow nodes by using the graph theory principle according to the space topological structure established in the step S1
Lower correlation matrix related to hydraulic and thermal parameters of outflow nodeA(ii) a The upper incidence matrix
Is a matrix of the order of Y X X,
for the upper association matrix
If cold fluid flows into the associated node i through directed pipe segment j, then the matrix is associated at the upper level
In (1),
otherwise
1≤i≤Y,1≤j≤X；
The lower incidence matrixAIs a matrix of the order of Y X X,
for lower association matrixAIf cold fluid flows out of the associated node i through directed pipe segment j, then the matrix of associations is in the lowerAIn (1),
otherwise
1≤i≤Y,1≤j≤X；
The hydraulic parameter is flow Q, the thermal parameter is temperature T,
multiplied by the pipe segment parameter column vector, equal to the parameter column vector flowing into each node,Amultiplying the parameter column vector of the pipe section by the parameter column vector of each outflow node;
s3, establishing a node heat flow balance equation and a directed pipe section heat flow balance equation according to the upper and lower incidence matrixes generated in the S2, and establishing a mathematical model;
s4, determining the heating power working condition calculation initial condition of the cold net according to the design working condition;
s5, solving a matrix equation set of the cooling network thermal condition calculation model by using a Gaussian elimination method to obtain the thermal condition adjustment condition of each node;
s6, when the outdoor temperature is adjusted or the local working condition of the cooling network is adjusted, the total circulation flow of the cooling network is controlled in an optimized mode, the backwater temperature of the whole cooling network is guaranteed to be kept at the design temperature, and the whole cooling network cooling system is optimized;
and S7, when the outdoor temperature is adjusted or the local working condition of the cold net is adjusted, repeating the steps of S4-S6, calculating the thermal working condition adjustment condition of each node, and adjusting the operation of the cold net system according to the parameter change to achieve the effect of optimizing energy conservation.
2. The method for optimizing the cooling of the distributed energy resource cooling network based on the graph theory as claimed in claim 1, wherein in step S1, the spatial topology of the cooling water network is composed of a cooling source, a water supply network, a water return network and a cooling user.
3. The graph theory-based distributed energy source cold supply network cold supply optimization method of claim 1, wherein in step S3, the node heat flow balance equation is:
in the formula
The sum of the heat flows of the associated branches into the associated nodes; q is the heat flow column vector for the directed pipe segment flowing into the associated node, q ═ q 1 ,q 2 ,…,q j ,…,q X ) T ，q j The heat flow which flows into the associated node from the directed pipe section j is shown, and the heat flow takes a positive value;A(q- γ) is the sum of the heat flows out of the associated node for the associated leg; gamma is the input or output cold load column vector on the directed pipe section, gamma is (gamma) 1 ,γ 2 ,…,γ j ,…,γ X ) T ，γ j The input or output cold load on the directed pipe section j is positive, and the output is negative;
q is represented by the formula: q ═ G c T c ；
In the formula T c Is a column vector of temperature at the end of a directed pipe section, T c ＝(t c1 ,t c2 ,…,t cj ,…,t cX ) T ，t cj Indicating the temperature of the j end of the directed pipe section; g c Is X order diagonal matrix, and its diagonal element G jc Is the product of j flow of directed pipe section and specific heat capacity of cold fluid, i.e. G c ＝diag(G 1c ,G 2c ,…,G jc ,…,G Xc ) T ；
γ is represented by the formula: y ═ H (T) w -A T T)；
Wherein H ═ diag (H) 1 ,h 2 ,…,h j ,…,h X ) Is an intermediate variable matrix, and in the cold user section, H is related to the comprehensive heat transfer coefficient of the building, the heat transfer area of the building and the air flow passing through the outer side of the fan coil, H j For elements in the intermediate variable matrix H, in pipe sections not connected to cold users, H j 0; t is a cold network node temperature column vector, and for a network line graph with Y +1 nodes, if the cold network water supply temperature is selected as the reference node temperature, T is (T ═ T) 1 ,t 2 ,…,t i ,…,t Y ) T ,t i Is the cold net node i temperature; t is W Is an outdoor temperature column vector of X1 order, T W ＝(t w ,t w ,…,t w ,…,t w ) T ，t w Expressed as the outdoor temperature.
4. The method for optimizing cooling of a distributed energy cooling network based on graph theory according to claim 3, wherein in step S3, the heat flow balance equation of the directed pipe sections is divided into three parts:
the first part, on the premise of not counting heat loss of the pipe section, except for the cold source of the cold supply system or the pipe section where the cold user is located, the end temperature of the directed pipe section is the initial end temperature of the directed pipe section, namely:
DA T T＝DT c
wherein D is diag (D) 1 ,d 2 ,…,d j ,…,d X ) As a matrix of intermediate variables, d j Is the element in the intermediate variable matrix D, when the element is the pipe section of the system cold source or the refrigeration user, D j Not more than 0, otherwise, d j ＝1；
And in the second part, for the pipe section where the cold net user is located, the cold net cooling capacity is equal to the cold load of the user, namely:
H(T w -A T T)＝EQ c (T c -A T T)
wherein E ═ diag (E) 1 ,e 2 ,…,e j ,…,e X ) Is a matrix of intermediate variables, e j Is an element in the intermediate variable matrix, e when it is the section of the pipe where the refrigeration user is located j 1, otherwise, e j ＝0；Q c For the circulating water flow of a single cold user, the initial value is the designed circulating water flow Q of the single cold user c0 According to the adjustment parameter pair Q c The cold net is changed, so that the aim of adjusting the cold net is fulfilled;
the third part, to the pipeline section that the system cold source belongs to, it is equal to cold source export water supply temperature to have the pipeline section end temperature, also when not counting cold net pipe section cold volume loss, cold net water supply temperature also is cold user's entry temperature promptly:
MT g ＝MT c
in the formula, T g ＝(t g ,t g ,…,t g ,…,t g ) T Is a Y x 1 order matrix, t g Represents the temperature of the cold net feed water, M ═ diag (M) 1 ,m 2 ,…,m j ,…,m X ) Is a matrix of intermediate variables, m j Is an element in the intermediate variable matrix, and when the directional pipe section j is the pipe section where the system cold source is located, m is j 1, otherwise, m j ＝0。
5. The method for optimizing cooling of a distributed energy cooling network based on graph theory as claimed in claim 1, wherein in step S4, the calculating initial conditions of the thermal condition of the cooling network includes: the water supply temperature of the front cooling network is changed, the indoor temperature of the front cooling user is changed, the outdoor temperature of the front cooling user is changed, the circulating water flow is designed by a single cooling user, the cooling load is designed by a single cooling user, the comprehensive heat transfer coefficient of the building, the heat transfer area of the building and the air flow passing through the outer side of the fan coil are changed, and the water temperature of the outlet of the fan coil of the front cooling user is consistent with the return water temperature of the front cooling network.
6. The graph theory-based distributed energy source cold supply network cold supply optimization method according to claim 1The method is characterized in that in step S5, the node heat flow balance equation and the directed pipe section heat flow balance equation form a matrix equation set comprising X + Y independent equations, according to the known conditions in step S4, the number of unknowns in the matrix equation set is X + Y, and the matrix is correlated
AndAthe system of equations has a unique solution, determined by the topology; the Gaussian elimination method is used for solving the solution of the linear equation set to obtain the adjustment conditions of the indoor average temperature of the cold user, the outlet water temperature of the fan coil of the cold user, the return water temperature of the cold network after being changed and the total load of the cold source after being changed, the adjustment condition of the total load of the cold source is calculated according to the return water temperature of the cold network after being changed, and the more the equation equations are, the more the time is saved.
7. The method for optimizing cooling of the distributed energy resource cooling network based on the graph theory as claimed in claim 1, wherein in step S6, when the temperature of the design water supply and return of the cooling network is determined, the total circulation flow rate of the cooling network supply is changed along with the change of the cooling load of the cooling network:
in the formula Q c total Is the total circulation flow of the cold net, W s The cooling load supplied to the cooling network, C Water (W) Is the specific heat capacity of water, t g ，t h Respectively the water supply temperature and the water return temperature of the cold net after being changed.
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